The dosage, i.e., the quantitative metering, of fluids from fluid sources and in particular the dosage of liquids from reservoirs, containers, vessels, conduit systems and other liquid sources by means of a shut-off device as such corresponds to the state of the art which has been known for a long time. Examples therefor are the filling of vessels with predetermined amounts of gases or liquids, the feeding of dosed fluid amounts into conduit systems or the free discharge of fluids from a fluid outlet, for example, the outflow of liquids such as water from an outlet tap or battery for rinsing or washing purposes.
Typical examples for conventional dosing systems in which mostly predetermined fluid amounts are metered or dosed, are to be found in washing machines and dish washers which are automatically filled with a predetermined amount of liquid, in washing and flushing systems, such as for water closets and urinals, in amount-limiting systems such as for showers and wash-bowls which are particularly used in railroads, in ships and airplanes, bottle and vessel filling machines, irrigating plants and automatic beverage dosing machines as well as for many other uses in the field of household, domestic appliances, sanitary techniques, food stuff technology, chemical technology (e.g., for dosing predetermined amounts of reactants or solvents for carrying out chemical reactions, for carrying out mixing and dosing procedures), and many others.
According to the state of the art the reproduction of a fluid amount is carried out in its simplest form by operating a shut-off device, such as a water tap, by an operator, i.e., by opening and subsequent closing after the outflow or delivery of a predetermined desired amount which may be determined via the mass, the weight, the volume, the level as well as via analogous variables.
The filling of a cooking pot or a bath tub with water are typical, common examples for such a dosing to be carried out directly by a person himself, with the dosed amount being individually determined, and being reproduced individually.
The simplest constructions of automatic dosing systems like the above-indicated systems are based on an allocation of flow rate and time: the fluid amount to be reproduced corresponds to an allocated open time of a time-controlled shut-off device. Examples therefor are automatic drink dispensers delivering, upon operation of operating means, selectable predetermined and reproducible liquid amounts.
However, the accuracy of these time-controlled dosing systems is dependent on how constant and reproducible the flow rate from the fluid source through the shut-off device can be kept.
On account of the influence of pressure variations, temperature variations, and thus, density variations, variations of the cross section, for instance by depositions such as calcification etc., alterations of the opening and closing time of the shut-off device caused by drift effects of the electric or electronic driving as well as by a mechanical play, of a changed pressure drop at the outlet and similar effects, time-controlled dosing systems are not particularly precise, and, above all, in respect of the dosed amounts they are not constant in time. In addition thereto, the selection of amounts to be dosed though a corresponding time setting cannot be easily carried out by an operator. For this reason, in drink dispensers only a few preset liquid discharge amounts are usually provided by the producer which are selectable but not changeable.
The closing operation of the shut-off device (which, for instance, had been opened by an operator or automatically) may be controlled via a detection of the level within the vessel to be filled which may be carried out for instance mechanically by means of floats, the hydrostatic pressure, acoustically by means of acoustic or ultrasonic detectors, respectively, or optically.
The accuracy of volumetric dosing is especially limited because of the temperature dependence of the fluid density.
In addition, also the mass or weight corresponding to a given level or volume amount may be determined.
More complicated and more accurate dosing systems are based on a direct measuring detection of a fluid amount flown through a flow meter and the closing of the shut-off device when a predetermined fluid amount has been reached. In this technical field, apart from mechanical flow meters, magneto-inductive flow meters, vortex (Karman) flow meters, ultrasonic flow meters and mass (Coriolis) flow meters are mainly used.
From DE-A-35 18 645 and from patent application DE-A-35 46 550 divided out therefrom a method and a circuitry for the control of sanitary mixer batteries for cold and warm water are known, by means of which the temperature of the mixed water is controlled with the flow rate of the mixed water being maintained constant.
Therefor, at least two set values serving for the electromechanical setting of the cold and warm water supply are derived from the difference between theoretical and actual temperature such that the resulting flow rate is maintained constant.
From the partial flow rates which are proportional to the corresponding set values an instantaneous cumulative filling amount may be determined by integration which is then compared with a preselected, predetermined cumulative filling amount; the dosing will be terminated when the instantaneous cumulative filling amount corresponds to the preselected cumulative filling amount.
In this previously known liquid dosing system a selected cumulative filling amount, i.e., the total amount of the liquid mixture to be dosed, may be fed into the system and retrievably stored therein.
According to this previously known technique the information on the cumulative filling amount to be stored therein, if necessary, will directly be input as an amount information through input means by an operator. Preferably, standard values are stored for the cumulative filling amount.
As far as the storage of the information on the total amount to be dosed is concerned, this previously known dosing system in principle differs for instance from the known drink dispensers reproducibly delivering fixedly predetermined liquid amounts, only in that the total amount of liquid to be dosed reproducibly may be freely selected and input by an operator.
However, up to the present, there are no dosing systems known allowing a free selection of a fluid amount to be dosed repeatably, which may be easily input or adjusted and be easily changed, and allowing the repeated reproducible delivery of this fluid amount without the necessity to enter this amount quantitatively in the sense of a corresponding input of a respective absolute value (e.g., in liters, kilogrammes, etc.).
Apart therefrom, in the state of the art there are not existing systems, which, beyond the above-indicated storability and requestability of constant delivery amounts of fluid, would be able to learn the storage information from an optional, once "predosed" fluid amount and thereupon reproducibly deliver that fluid in an amount corresponding to the stored information in a repeatable manner.